Chapter 2

1. Chapter 2 Problem Solving Tools for Methods Engineering

2. Our Text Book Website: • http://highered.mcgraw-hill.com/sites/0072468246/

3. Outline for today • A short history of Human Factors and Ergonomics, • Methods Engineering/Work Design • Example of Methods Engineering • Discussion of in-class exercise, • Approaches for both physical and “thinking” tasks,

4. A Short History of Human Factors and Ergonomics

5. Methods Engineering • Technique for: • Increasing production per unit of time. Example: increasing the number of customers that can be handled per cashier by installing bar code readers. • Decreasing cost per unit output. Example: decreasing total cost of each cell phone by reducing the number of parts and thus the labor hours required for assembly. It is critical to look at impact on whole system.

6. Methods Engineering Focuses Primarily on improving productivity though (re)design of: Motivation: Incentives/rewards Organizational structure Work Process Work operations Tools (Products) Work environment

7. Methods Engineering • Often used synonymously with: • Corporate re-engineering • Work design • Operation analysis • The difference between these terms in the level of detail. Big picture level Detail level

8. Select project I.D. product or service experiencing difficulties. Get and present data Study situation, take measurements to determine where difficulties really lie, Analyze the data: Figure out which of many problems are most critical Develop ideal method(s) Identify alternative approaches which may address most critical problems. Present and install method at the work site Develop a job analysis To insure operators are adequately selected, trained, rewarded, etc. Establish time standards Establish fair and equitable standards for work performance. Follow up the method Take measurements to determine if changes really did improve situation as predicted. Methods Engineering

9. Example: Mission Planning and control for the Mars Exploration Rover • Researchers introduced automated planning tool, MAPGEN • Tool had to fit with users’ existing way of thinking about plans, • Introduction of new tools caused the planning process to change, • Product and processes were evolved together, over time.

10. Many methods can be used in many stages of the design process A typical spiral designprocess Prototype Testing Requirements Gathering Final Performance Evaluation or Comparison Design Specification Design Review

11. Problem Solving Tools for Methods Engineering: help to identify what the most important problem is • Observational tools: • Site walk-thrus • Observation and interviews of workers and managers • Ethnographic studies

12. Problem Solving Tools for Methods Engineering (Ch. 2.1) • Exploratory tools • Pareto Analysis (Vilfredo Pareto) • Fish Diagrams (from Japan, 60’s) • Gantt and PERT charts (40’s wartime).

13. Pareto Analysis • Items of interest are identified (e.g. types of product flaws that result in scrapped parts, time spent on each activity required to manufacture a product or perform a service. • Items are measured on a common scale (such as frequency total cost, total time, etc.) • Items are ordered in descending order

14. Example of a Pareto Chart

15. Example 2 Pareto chart: worker time study

16. Example of a Fish Diagram

17. Fish Diagrams • Cause and effect diagrams • Effect is a problem = “fish head” • Causes = “fish bones” • Typical causes: • Environment • Methods • Materials • Administrative • Machine • Human

18. Gantt Charts • Activities shown as bars with: • Anticipated start times • Anticipated completion times • Actual start and completion times • Use a vertical line to show current time • May use color codes to show various things: • Completed activities (grey) • On going activities, on schedule (green) • Overdue activities (red) • Almost over due activities (yellow)

19. Example of a GANTT chart

20. PERT Charts:Program Review and Evaluation Technique • Project networks • Like Gannt charts, PERT charts show activities, start and end times • Also show variation in activity durations: optimistic, average, pessimistic, • Show dependencies between activities, • Can identify a critical path (longest path) that constrains minimum completion time of whole project, • Analyze how “crashing” activities can shorten duration of whole project.

22. Example of a PERT chart

23. Problem Solving Tools (cont.) • Recording and Analysis tools: • Operation Process Chart • Flow process chart • Flow diagram • Worker and Machine Process Charts • Gang Process charts • Synchronous servicing

24. Operation Process Charts • Chronological sequence of operations • Show operations as a flow chart though the worksite. • Show the types of operations: • Operation • Transport • Inspection • Delay • Storage • Decision

25. Operation Process Chart: Manufacture of a telephone stand

26. Flow Process Chart • More detail than Operation Process Chart: • Not usually used for entire assemblies, • Used for just one component (or operator) • Add in information on: • Operation duration (time to complete) • Distance traveled (for transport operations) • Good for showing savings of a new method.

27. Flow Process ChartPreparation of direct mail advertizing

28. Flow Diagram • Show layout of work area • Show the flow of work through that area • Show congestion areas, crossing worker paths, total travel. • Identify how layout can be redesigned to reduce travel, motion, collisions, etc. • Store materials near where they are used. • Increase efficiency and safety.

29. Flow diagram

30. A revised and more efficient flow diagram

31. Worker and Machine Process Chart • Show one worker, many processes • Identify idle time for each, • Reorganize operations to reduce idle time. • Identify how many machines worker can manage

33. Gang Process Charts • Show one machine, many workers, • Identify idle time for each, • Re-arrange tasks between workers to reduce idle time.

36. Synchronous and Random Servicing • Synchronous servicing: operations (usually done by machine) take a predictable amount of time, so the operator(s) “servicing” actions can be synchronized with the machines’ cycle times. • Random servicing (Asynchronous): operation occurrences happen with some unpredictability: e.g. machine breakages, field service calls, etc.

37. Synchronous Servicing n ≤ l + m l + w The number of Machines an operator Can be assigned: Where: n = number of machines operator handles l = total operator loading and unloading time m = total machine running time w = worker time between machines.

38. Example • Should n be 3 or 4? • Figure out how much it costs per unit of production if: • 3 machines are assigned to each worker • 4 machines are assigned to each worker • Choose the assignment that is least expensive.

39. Random Servicing • This method applies when you have one person handling several machines (or things) that: • Do not run for a set length of time, • Need servicing at irregular intervals • Examples: • Machine repair: machines break at random times. • Call center, calls come in at random times.

40. Random Servicing: Approach • The proportion of time, p, that a machine is up or down can be estimated through a time study(Chapter 9) or a work sampling study(Chapter 14) • q = 1 - p • P= the probability that m out of n total machines are down is: P (m of n) = n! x pm qn-m m! (n – m)!

41. Random Servicing: Example • Suppose at a call service center you have one phone operator to answer: • n = 4 phone lines • p= 0.10 = probability that a phone line is in use is. • q= 1 – p = 0.9 = the probability that a given phone line is unused, e.g. no one on the line. • “In use” means that a caller may be either: • waiting on the line, or • speaking with the phone operator. • If calls come into the center at random, what is the probability that there will be exactly three phone lines in use? (e.g. One caller speaking with the operator, two callers waiting).

42. Random Servicing: Example • No callers 4! x (.10 ) (.94) = .66 0! (4 – 0)! • One caller 4! x (.11 ) (.93 ) = .29 1! (4 – 1)! • Two callers 4! x (.12 ) (.92) = .05 2! (4 – 2)! • Three callers 4! x (.13 ) (.91) = .0036 3! (4 – 3)! • Four callers 4! x (.14 ) (.90) = .0001 4! (4 – 4)!

43. Random Servicing: Example In other words, in this situation: • 66 % of the time, the sales assistant has no calls; • 29 % of the time, exactly one call; • 5 % of the time, exactly two calls, e.g. the assistant helps one customer while one customer waits,  • Less than a half a percent of the time (0.36 %), exactly three calls: one customer is being helped while two customers listen to Musak.  • The probability that all 4 lines are in use at once is almost non-existent.

44. Coffee Shop Study • No studies had been done previously at this company to assess current efficiency • Goal: to identify any way possible of improving productivity, • Initial request: do a time study at 3 very different stores, improve productivity of coffee making process. • Corporate goal: customer should be in and out within 3 minutes, “door-to-door”.

45. Observational tools • Site walk-thrus: look at layout, tools equipment, how they are used. • Interviews of workers and managers to identify what they view as problems, • Ethnographic studies: observe work in detail as a “fly on the wall” as it normally occurs in its normal setting, possibly over a long period of time. Good for observing interactions between workers. • Time and/or motion studies: to learn detail about what people do and how long it takes.

46. Job Worksite Analysis Guide • Check list of items to think about/examine while touring jobsite: • How do parts/products flow in and out? • What kinds of motion are involved? • Are any tools being used? • Were there awkward motions? • Is worker fatigued? Stressed? • Is there decision making?

47. In a time study: Often applied to large or small tasks, Work is observed Work is broken into “elements” Each element is timed, The process is re-engineered to be faster, safer, less error-prone, etc. In a motion study: Often applied to fine-grained continuous motions, Motions are observed in performing a task, Motions are be divided into “therbligs” The process is re-engineered by: eliminating unnecessary motions, re-sequencing motions. Time and Motion studies The two are often combined.

48. Tools for Time and Motion Studies • Tools can be simple and low cost: • Stop watch, • Pen and paper, • Maybe a video camera. The task determines if it is necessary. • The technique is low-tech, but can still result in major cost savings!

49. How did your group speed up your assembly process? • Use multiple packers, • Use two hands, • Lay-out pieces in advance in order of assembly, • Orient each object in correct position in advance, • Sequence objects to be easier to pack, • Fewer objects = less material handing = time savings!

50. What about thinking tasks? • Time and motion studies apply to physical aspects of the task and physicalobjects. • What about the psychological aspects of a task? How can one study “thought work” and apply factors to improve the work of people who do: driving, design, planning, management, and decision making?